Method of and means for transforming direct current.



1. C. LINCOLN.

METHOD OF AND MEANS FOR TRANSFORMING DIRECT CURRENT.

APPLICATION FILED FEB. 2. i912.

Patented May 29, 1917.

2 SHEETS-SHEET 1.

I r a 4 J. C. UNCOLN.

METHOD OF AND MEANS FOR TRANSFORMING DIRECT CURRENT.

APPLICATION HLED FEB-2,19I2.

2 SHEETS-SHEET 2- Patented May 29, 1917.

. UNITED STATES PATENT OFFICE.

JOHN C. LINCOLN, OF CLEVELAND, OHIO, ASSIGNOR TO THE LINCOLN ELECTRIC COM- PANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

METHOD OF AND MEANS FOR TRANSFORMING- DIRECT CURRENT.

Specification of Letters Patent.

Patented May 29, 1917.

Application filed February 2, 1912. Serial No. 674,892.

To all whom it may concern:

Be it known that I, JOHN C. LINCOLN, a citizen of the United States, resident of Cleveland, county of Cuyahoga, and State of Ohio, have invented a new and useful Immeans for transforming direct current, its

object being to effect such transformation with a. minimum loss of power. A specific object of the invention is to utilize such transformation in connection with the use of the electric are for welding, electric arclighting and other similar purposes.

T 0 this end, my invention consists of a method and means hereinafter fully described and particularly set forth in the claims.

The annexed drawings and the following description set forth in detail one mode of carrying out my invention, the described mode, however, constituting but one of various forms in which the principle of the invention may be applied.

In said annexed drawings:

Figure 1 illustrates diagrammatically a transformer embodying my invention and connected with an arc-circuit.

Fig. 2 is a diagram showing connections with a transformer embodyingmy invention and arranged to manually control the current at the arc.

Fig. 3 is a simplified diagram of the arrangement shown in Fig. 2.

The embodiment of my invention in so far as relates to the means for transforming direct current, comprises a central rotary armature A, a field structure B, and a circuit J arranged so that the current therein may be applied for the purpose of welding or-repairing castings.

This field structure is provided with four poles, each of which is divided into two parts, a part C of lesser crosssect'ion, and a part C of greater cross-section. The poleportions C of greater cross-sections have two field-windings upon them, a winding D of comparatively high resistance, and a winding E of comparatively low resistance. The pole-portions C of smaller cross-section have wound upon them windings D of reslstance similar to that of the windings D, in series with the latter and connected with the main brushes F and F. Thesewindings D and D are therefore connected in shunt 1n the apparatus.

The windings E of low resistance are in series with each other, a secondary brush G and an exterior arc-circuit J. This secondary brush is located so as to be intersected by a plane passingthrough the axis of the armature A and midway between the two pole portions C and C'- For the purpose of illustration, I will assume that the supply current in the main lines H H is of 220 volts, and that it is required that a maximum voltage of 110 be obtained at the arc. To obtain this result, I make the cross-sectional area of the pole portions C one-half that of the pole-portions C and provide one-half the number of ampere turns of winding D on the pole portions C as are provided upon the pole-portions C.

The difference of potential at the brushes F and F would therefore be 220 volts, and the current passing through the shunt field will remain constant under all conditions. The connections are furthermore such, as will be observed, that the difierence of potential between the brushes G and F is substantially equal to the difierence of potential between the terminals in the arc-circuit J 4 i. 6., between the movable terminal or carbon K and the casting K. It therefore follows that any change in the difference of potential between these'two brushes is accompanied by a similar change in the difference of potential between said two terminals.

Let'it first be assumed that current is being supplied to the transformer but that the terminals K and K areseparated so that no arc is being formed. Under these conditions the current is flowing through the shunt-windings D and D only. A divided magnetic field is thus created between each complete pole and the armature, which field consists of two parts,-one between pole-portions G and the armature, and one between pole-portions C and the armature.

the flux per square inch from pole-portions low resistance.

C-is twice that per square inch from poleportions' C, but the total flux from the one pole-portion isequal. to the total flux from the other. The diflerence'of potential between brushes F and G being proportional to the flux from the small pole-portion C, the voltage at the arc terminals is there'- fore 110, the amperage being zero. 7

Let it now be assumed that the main line is supplying a current of 220 volts to the field-and armature, and that the terminals K and K are in contact, the arc-circuit being therefore short-circuited. A current will, hence flow from the brush F through the armature windings subtended by the brushes F and G, through the arc-circuit,

and through the series windings E. The introduction of the brush G, however, will also provide a circuit for a generated current which will be set up by the armature windings subtendedby the brushes F and G. This circuit includes also the serieswinding E and are circuit J which are of When the brushes F and G are short-circuited through the series winding and terminals K, K, there will be a heavy generated current and a large motor current which will combine to produce an armature pole at the point G in the armature' The connections are such that this pole is of the same sign as that produced by the shunt'windings D and D on the poles C and C. When this armature pole is strong enough, there will be no net flux from the pole C. The series winding on the pole C is provided for the purpose of strengthening this pole as the generated current increases. By, this means the flux 1s transformed from the pole C to the pole C with an increase in the current in the arc circuit.

Also as before, the magneto-motive force due to the 'shunt windings D exists, and the resultant flux is, in the illustrated device and as previously stated, substantially onehalf per square inch of area of that flowing from the pole portions C. The series windings E, however, are in the samedirection as the shunt windings D, and are of a nature such that the current passing therethrough sets up an additional flux substantially equal to that which would flow from pole-portions C under conditions of no current in the arc-circuit. The difference of potential therefore, between the brushes F and Gbec omes 220 and the total flux gained in ,the magnetic zone between-the pole-portlons C and the armature is substantially equal 1n amount to the flux lost in the magnetic zone between the pole-portions C and the armature. Thetotal flux, therefore,

I prefer to arrange the windings in a manner such that the increase in flux due to the current flowing through the series-windings will be greater than the decrease ih flux from pole-portions C, so that the arma-' ture will slow up when 'the terminals are caused to short-circuit the circuit J, for the'purposes of safety, by avoiding any possibility of the motor running away.

Let "it now be assumed that the movable terminal or carbon K is withdrawn from the casting and an arc formed. The effect of this withdrawal is to increase the resistance between the two arc terminals, and consequently to decrease the amount of current flowing through the arc-circuit, which means that the amount of current flowing through the series-windings is also decreased. The result of this is that first, the counter-magneto-motive force due to the arc current is reduced and the magnetomotive force establishing. the flux from the pole-portions C to the armature overbalances this counter-magneto-motive force, so

that the net result is a positive flow of mag-' tially in the same proportion as the field betweenthe pole-portions C andthe armature is strengthened. The voltage between the brushes F and G, becomes of a quantity expressed 'by a figure less than 110, and which I will assume .by way of illustration- .is 50 volts.

Let it now be assumed that the working conditions are such that the movable terminal or carbon K is still further removed from the casting and the resistance is still further increased in consequence thereof. The result of this will be to still further strengthen the magnetic field between the pole-portions C and the armature, and correspondingly weaken the magnetic field be tween the pole-portions C andthe armature, thus increasing the difference of potential between the brushes F and G, and correspondingly increasing the difference of potential between the terminals in the arc circuit. An increased resistance at the arc, therefore, is accompanied by an increased voltage and which is the desired end to be attained. This resistance may, therefore, be increased until the two portions of the. divided magnetic field become of equal strength and the difference of potential between the brushes F and G becomes 110,- z. 6., equal to the difference of potential between the brushes F and G, which is themaximum voltage which may be obtained at the are without having the latter blow out.

The above described device is suitable for use in connection with successive operations of welding or. repairing which present sub-.

. stantially constantly recurring like condikeep the voltage as low as possible in order to reduce the consumption: of power. On the other hand it is desirable to keep the are as long as possible in order to prevent the material of the negative electrode from being transferred to the material to be oper-- :ated upon, as in the case of a carbon negative' electrode operating in connection with steel castings. Such-castings are usually required to be as free 'as' possible from hardness, and when the arc'is too short, such carbon is transferred to the casting and under the influence of the attending heat produces a high-carbon or hard steel, which is to be avoided.

A normal voltage should therefore be selected which will combine the above re- I quired conditions to the greatest and the undesirable conditions to the least degree. Ex-

' perience has-shown that 50 volts will produce the best compromise between the above .two conflicting sets of requirements, and I have therefore adopted that as the normal voltage 'at the arc.

The said embodiment of my invention illustrated in Fig. 1 is arranged so that the relation of amperage to voltage will be repthe difference in flux from the small poleportions and the large pole-portions to change-with greater or less rapidity, relatively to the amperage at thearc, so that the .normal voltage obtained at the arc maybe coincident with a greater or less amperage in the arc circuit.

Fig. 2 shows, by Way of illustration. the

connections and arrangement whereby I get a normal voltage of 50, and an amperage of one-quarter, one-half, three-quartersand the full maximum of 400 amperes in the are- It will be readily understood by circuit. those skilled in the art, however, that the connections may be so varied or amplified that any desired proportion of the maximum current may be-obtained' having the as-' fiivsumed normal voltage of 50.

In order to obtain this desired result, I

arrange the connections and field windings as they are diagrammatically illustrated in said Fig. 2. In the arrangement both poleportions are provided with the shunt-windings D and D, and the larger pole-portions with the series-windings E, the functions of which are precisely those of the analogous elements in the apparatus illustrated in Fig. 1. In addition, however, I provide an additional winding E on each small pole-portion and connect them with the series-windings E as hereinafter described. An external resistance R is introduced'in the circuit together with the switches #1, #2 and #3.

These switches are provided and arranged so that their manipulation will give the fractions of or the whole of the maximum current desired, in this instance 100, 200, 300 and 400 amperes, as will hereinafter appear. The single-throw single-pole switch #1 makesand breaks connection with the two terminals f and f; the single-throw double-pole switch 2 makes and breaks connection with the terminals 9 g and g g. The double-throw double-pole switch #3 may connect terminals h It with terminals h h or it If. 1

'When the lowest amperage at the are, 100 amperes in this instance, or what I shalldesignate as adjustment number 1, is desired, switches 1 and 2 are opened so as to break the corresponding circuits and switch 3 i thrown into its first or down position as shown in full lines in Fig. 2.

In this position of the switches the serieswindings E and E are all in series with each other as may be readily seen by an inspectionof Fig. 3. The connections and relationship of the parts may be exactly defermined from an inspection of Fig. 2 which is a complete wiring diagram. Referring to this figure, the current comes from the main line, passes through the starting box L, and passes into the line Z, from which it flows together with the current generated in the arm ature'winding, passes through the armature into brush G, through connection Z, into connection Z and into the upper two of the four series-wlndings E E, through the medium of connection Z through connection Z, it reaches one of the terminals h, whence it passes, through switch #3 into one of terminals 7L through connection Z the series-coils E E E E succesinto the main brush F. From the latter it,

From the latter I sively, andconnection Z, to the other terminal 71?, through switch #3, to the remaining two coils E E, through the medium of connectionZ. From the left-hand lower coil E, it then passes through connection Z to the arc-circuit J From the latter it reaches terminal Z of switch L where the motorportion of the are current passes into the other main line H, the generated-portion thereof passing through connection 1 to the other main brush F, and thence through the armature to brush G, thus completing the circuit. .The direction of the current through the series-windings E is such that, when the connections are as just described,

' it will set up a magneto-motive force counter to that set up by the shunt-windings D, so that these small pole-portions may be described as differentially wound. The effect of such counter or opposing action will be to reduce the net flux from the small porbe the normal or approximately 50 volts.

By now throwing switch #3 in the other or up position as shown in dotted lines in Figs. 2 and 3; adjustment number 2 is ob tained in which the windings E are entirely out outfand the our windings E connected two each in series and the two sets in parallel. In this case, the current takes the path described in connection with adjustment number 1 until it reaches the terminal 72., in

which course it has passed through the two Instead of passingupper coils E E. through connections Z however, which before made the series connection with the coils E E E E, it passes directly into the arc-circuit through the medium of terminal h and connection Z Theswitch being in the described position, the current also passes from connection Z to the other terminal h, connection Z and so through the two lower coils E E in series through connection i into the arc-circuit as before. All opposing action of the windings E is hence eliminated and the magnetic reactions are similar to those described in connection with Fig. 1. As compared with theresult'obtained in adjustment number 1, the action of the serieswindings D becomes one-half as strong for a given current since the coils E are now connected in series parallel. A corres 0nding increase of current at the arc is e ected for said given or normal voltage, so that the normal voltage being still 50 but the amperage being 200, the volt-ampere curve is less markedly drooped in character than in the case of adjustment number 1.

By now leaving, switch #3 up and closing switch 1, the resistance R is introduced in parallel with the series-windings E, which are left in series-parallel, windings E being still cut out.

The connections are now precisely those described with relation to adjustment number 2, excepting that current now passes from right-hand terminal it through connection Z through said resistance R and so into the arc-circuit. This resistance is of a ment (when the resistance R is in parallel) with the fields E which are in series-parallel as the corresponding relation which has al ready been described in connection with the device illustrated in Fig. 1.

Switch #2 being now closed, the conditions remain as just described excepting that the series-coils E are re-introduced into the circuit but the direction of the current flowing therethrough is reversed. Instead of an opposing action therefore, these windings E augment the magneto-motive force created by the shunt-windings and consequently we have a still further increase in current for the normalvoltage at the arc, or 400 amperes, the maximum current.

Having fully described my nvention,

what I claim and desire to secure by Letters Patent is:

1. In a direct current transformer, the

combination of a field provided with symmetrically divided poles; an armature; main brushes; an intermediate brush; the windings on said armature being divided into two portions by the intermediate brush; part of the windings under one pole portion carrying a generated current; the pole portion opposite that part of the armature winding carrying the generated current being provided with a shunt winding and the other portion being provided with a shunt winding and a series winding, the series winding being in the circuit carrying the generated currentand so connected as to strengthen the corresponding pole portions as the generated current increases.

2. In a dynamo-electric machine, the combination of a divided-pole field-structure; an armature rotatably mounted in the field; an exterior circuit; means for shifting the flux from one pole-portion to another poleportion; and additional means for producing a given shifting of such flux with currents of various amperage supplied to said exterior circuit.

3. In a dynamo-electric machine, the combination of a divided-pole field-structure; each pole-portion provided with a shuntwinding and an additional winding; an armature rotatably mounted in the field; and switching mechanism whereby the additional windings on the part of pole-portions may be cut out of the circuit, and the additional windings of the other pole-portions may be connected in series-parallel in said circuit.

4. In a dynamo-electric machine, the com.- bination of a divided-pole, field-structure; each pole-portion provided with a shuntwinding and an additional winding; an armature rotatably mounted in the field; an exterior circuit connected with said armature; a resistance; and switching mechanism whereby the additional windings on part of the pole-portions may be cut out of the circuit, the additional windings of the other pole-portions may be connected in series-parallel, and the said resistance also connected in parallel with said series-parallel windings in the circuit.

5. In a dynamo-electric machine, the combination of a divided-pole field-structure; each pole-portion provided with a shuntwinding and an additional winding; an armature rotatably mounted in said field; means for connecting the additional windings on the one set of pole-pieces so that they augment the magnetic action of the shunt-windings on such pole-pieces; and means for adjustably connecting the additional windings of the other set of polepieces so as to augment or diminish the magnetic action of the shunt-coils on the same pole-pieces, according to the adjustment made.

6. In a dynamo-electric machine, the combination of a field-structure having poles each of which includes two divisional polepieces, one of which is of larger cross-sectional area than the other, each such polepiece being provided with a shunt-winding and an additional winding; an armature rotatable in said field; means for connecting the additional windings on the pole-pieces o of larger area so that they augment the magnetic action of the shunt-winding thereon; and means for adjustably connecting the additional windings on the pole-piece of lesser area so that they augment or diminish the magnetic action of the shunt-windings thereon, according to the adjustment.

7. lln a dynamo-electric machine, the combination of a divided-pole field-structure, each of which includes two divisional polepieces, one of which is of larger sectional area than the other, each pole-piece being provided with a shuntswinding and a series winding; an armature rotatable in said field; means for connecting the series windings on the pole-pieces of larger area so that they augment the magnetic action of the shunt-windings on such pole-pieces; and means for adjustably connecting the series windings on the pole-piece of lesser area so as to augment or diminish the magnetic action of the shunt-windings on such polepieces, according to the adjustment.

Signed by me, this 29th day of January,

JOHN C. LINCOLN. Attested by WM. ROTHENBERG, A. E. MERKEL. 

